Humans walk on two limbs with surprising economy. Our metabolic cost of walking is low among mammals, and exceptionally low when compared to our closest living relatives, the chimpanzees. The human-chimpanzee contrast implies strong selection for low cost walking since our last common ancestor, 6-7 million years ago. What aspects of human anatomical structure (i.e. bone and muscle-tendon size and shape) determine walking costs, and how did low cost walking evolve in hominins? Comparative paleontological studies provide important insight into the tempo and mode of skeletal evolution. But, understanding how individual skeletal traits influence the global functioning of the pelvis and hind limb during walking is a significant challenge.

Here, Dr. O'Neill advocates for the use of detailed 3-D musculoskeletal models with lab-based measurements of walking to address this challenge. He will present his ongoing work on the development of a 3-D musculoskeletal model of the chimpanzee pelvis and hind limb, as well as results from recent studies of chimpanzee muscle properties and 3-D mechanics during bipedal walking. Chimpanzee data are compared with matched datasets from humans in order to gain new insights into the anatomical basis and evolution of low cost walking in hominins. Some future directions for this new line of research will also be discussed.